The First Transcontinental Railroad is stopped dead near its starting point, both in the East and in the West. Repeated injunctions from the president of the STranscontinental Railroad are having no effect: His workers are constantly prevented from working by agents of a mysterious traitor. But Lucky Luke witnesses one of the acts of sabotage and stops it. Soon, he is in charge of security for the entire westward push ”and he will have his work cut out for him!

Isabella's first season in London is a disaster, with not a single offer of marriage. All possible suitors find her dull, while she believes none of the contenders for her affections are worth catching.